In mammalian animals, the heart is a hollow muscular organ having four pumping chambers: the left and right atria and the left and right ventricles, each provided with its own one-way valve. The natural heart valves are identified as the aortic, mitral (or bicuspid), tricuspid and pulmonary valves, and each has leaflets to control the directional flow of blood through the heart. The valves are each supported by an annulus that comprises a dense fibrous ring attached either directly or indirectly to the atrial or ventricular muscle fibers. Various surgical techniques may be used to repair a diseased or damaged valve. In a valve replacement operation, the damaged leaflets are excised and the annulus sculpted to receive a replacement valve, or in some cases the valve implants over the native leaflets.
Heart valve prostheses are either of the mechanical type that uses a ball and cage or a pivoting mechanical closure, or a tissue type or “bioprosthetic” valve typically constructed with natural-tissue valve leaflets. In bioprosthetic valves the leaflets function much like in a natural human heart valve; imitating the action of the natural leaflets to coapt against each other and ensure one-way blood flow. A whole xenograft valve (e.g., porcine) or a plurality of xenograft leaflets (e.g., bovine pericardium) provide occluding surfaces that are mounted within a surrounding stent structure, typically having commissure posts extending downstream or in the outflow direction. Research is ongoing on synthesizing the tissue leaflets, and therefore the term “flexible leaflet valve” may refer to both bioprosthetic and artificial valves. In both types of prosthetic valves, a biocompatible cloth-covered suture or sewing ring is provided, on the valve body for the mechanical type of prosthetic valve, or on the inflow end of the stent for the tissue-type of prosthetic valve.
When placing a flexible leaflet prosthetic valve in the mitral position, the commissure posts are on the leading or blind side of the valve during delivery and implant, and the surgeon advances the valve down a parachute array of sutures that are pre-installed in the mitral annulus. The difficulty of the delivery task is compounded by the small access pathway into the left atrium. Suture looping sometimes occurs when one or more of the sutures in the parachute array inadvertently wraps around the inside of one or more of the commissure post tips. If this occurs, the looped suture(s) may slow down the implant procedure, damage one of the tissue leaflets when tightly tied down, or interfere with valve operation and prevent maximum coaptation of the valve leaflets, resulting in a deficiency in the prosthetic mitral valve.
One of the functions of many mitral tissue valve holders is to mitigate the potential for suture looping of the struts and/or cords during implantation. Existing devices on the market attempt to achieve this by moving the commissure struts toward the central axis of the valve (strut binding). For example, U.S. Pat. No. 4,865,600 to Carpentier, et al., provides a holder having a mechanism that constricts the commissure posts inwardly prior to implantation. The Carpentier device provides an elongate handle to both hold the valve/valve holder combination during implantation, as well as to cause the commissure posts to constrict inwardly. More recently, U.S. Pat. Nos. 6,409,758, 6,702,852, 6,964,682, 6,966,925, and 7,033,390 disclose heart valve holder systems that resist suture looping.